BEIJING — Ahead of the 20th anniversary of the bloody crackdown on Tiananmen Square this week, Chinese authorities rounded up dissidents and shipped them out of town. Now, they’ve even shut down Twitter.

Along with their usual methods of muzzling dissent, the authorities extended their efforts Tuesday to silence social-networking sites that might foster discussion of any commemoration of the events of June 3-4, 1989.

DENVER — Colorado energy regulators on Monday proposed tighter rules for shutting down oil and gas pipelines after a fatal explosion blamed on natural gas leaking from a line that was thought to be out of service but was still connected to a well. The Colorado Oil and Gas Conservation Commission rules govern flow lines, which carry oil, gas and...